One of the major advantages in using the carburetors is in it's throttle response. This is more apparent in the racing field where no filters or collectors are used in the intake.
As you may know, there are 4 throttle, fuel injection mechanism too. And the resulting principle is similar. The two systems do have very similar, and distinct advantage over the single throttle setup. The later model OEM 20 valve 4A-GE engines utilize the latter, 4 individual throttle, which we'll cover elsewhere in this website.
First of all, carburetors need no intervention of ECU's which can be both expensive and in most cases limited in adjustability, unless expensive alternatives like those programmable variety is in your budget.
The goal is to match the jets within the carburetors to the required spray pattern and volume to desired mixture at a given rpm and vacuum. There are usually main jets and sub jets for various compensation, both of which have to be manually setup. Second, the carburetors can be adjusted for much wider variety of engine setups using the same unit for the most part. Since the carburetor's adjustment is in the jets alone, it can accommodate almost anything you can imagine Well, some forced induction setups exited in the past but all of them are running fuel injection now.
Third and my favorite reason for the carburetors is the esthetics The setup simply looks really nice!!!! Once an addict, you'll never go back. Since carburetors work with very narrow, optimized range, the more you set it for peak performance in one area, the more you will run into substandard operation in other areas.
For example, the carburetors cannot compensate for difference in gasoline or effects of climatic temperatures and pressures on it's own. This adjustment is left to the owner to re-adjust each time. Though Mikuni's and other carburetors do operate very well in most conditions, the fuel delivery under many different conditions is usually much more accurate with modern electronic fuel injection. And usually much more efficient.
For those who likes to tinker or wants optimum mixtures for a narrowly focused field, this can be much fun. Certainly, you will get attention from those not so inclined when you fiddle with carburetors on the spot and get good results.
Race mechanics are often admired for such talent and gets gratification from that alone. But at the same time, it's certainly a chore for those who likes to me free of maintenance tasks or depend on it to commute every day. You must be frequently prepared to re-jet them or make adjustments when weather changes dramatically.
For sure, those who live in areas with drastic seasonal climate changes will have to make adjustments all throughout the year, to keep it in top shape, and sometimes even just to start the engine. Keeping the above precautions in mind, the carburetors are seriously rewarding piece of equipment, and once it is running correctly, it's hard to beat with even the best fuel injection in terms of response and torque output Some carburetor setups:.
Ceased production in , Mikuni is still widely available. One of the best all around units for it's drivability and performance. It may be the best all-around carburetors for use on daily driven vehicles. Kits are still available for the 4A-GE's and one of the easiest to setup. Definitely recommended for the first-timer. Increasing in popularity as Mikuni's becoming harder to obtain, the Weber is an excellent carburetor with very accurate fuel delivery at higher rpm.
Increasing in popularity as Mikuni's becoming harder to obtain, the Weber is an excellent carburetor with very accurate fuel delivery at higher rpm. Mechanically, it is easy to set and parts are widely accessible. Manifolds for the 4A-GE are widely available also. The Weber is also referenced by host of guidebooks so it's another recommendation for first-time users. The Weber's other advantage, especially over the Mikuni-Solex is it's design of the float, making the carburetors less prone to mixture changes in cornering and braking loads.
It's a little bit more nervous and unstable than the Mikuni-Solex over wide rpm ranges. The jets are available in smaller increments than Mikuni. It's a bit finicky for street use but what else do you expect from anything that comes from Italy It's fun and full of character. The FCR features include a progressive dual link throttle linkage for improved valve control enabling stable low- throttle operation.
The short venturi length offers quick response. These carburetors are producing very high horsepower rating on the 4A-GE and still has a nice ability to stabilize the mid range even with the use of highly aggressive cam profiles. The intake charge has less turbulence compared with butterfly-type venturi and is the carburetor of choice today in Japanese hobbyists.
The FCR's ability to resist miscalibration during cornering G's is unequalled, making use of it's motocycle heritage. The following section was submitted by Richard White, an expert data reference collected by a serious local 4A-GE enthusiast I know you have stated that you are in the process of putting together an article about side draft carbs for the 4A-G.
If you do not already have it, it appears to be a good reference source for those interested in this subject. At any rate, I would like to pass on what looks to be some key information on this subject. I have tried to summarize some of the key points and the many combinations of components that would most pertain to the 4A-G.
I hope it can be of use to your article. Longer rams are usually used to maximize mid-range response. Main jet: Main jet recommendations with ideal choke size: cc per cylinder. Note, over rich mixtures washes the oil film off the cylinder bores and causes high cylinder wear. The recommendations represent the rich side for the given applications so jetting down may be necessary for optimum results - but only after testing.
If the air corrector is too lean large dia. The air corrector is used to tune top end performance in a very narrow range. Beware of this fact when ordering auxiliary venturis. If the auxiliary venturi is not large enough the engine will falter at a certain point in the rpm range.
Find by trial and error the smallest pump jet that gives the best performance. The accelerator pump jets have to be large enough to remove any trace of hesitation or stumbling when the accelerator pedal is depressed but not more than this. Needle valve: 1. Use a 1. I'd link you the pages I got this info from but cbf. Need someone who has actually done it and knows what theyre talking about to reply. There was a guy in brisbane city whom I bought parts off, who had a single weber downdraft and locked 4ag dizzy on his ae71, pretty cool.
Last edited by undercoverninja; 12th May at PM. I have done a few this way and they sit in a lot further in than using an adaptor plate so there are less issues with it fouling on the headers. Hmm night have a look for one. PM if ya like. Pm sent.
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